Are your prints mounted? If so, you don't absolutely have to mat them although that is preferred. The main function of matting is to prevent contact between the glazing and the print surface. Depending on how long the prints remain framed, and the humidity, contact can damage the surface of the print. If you don't intend to leave the prints framed for very long, then you could take the chance of not matting them.
It's relatively easy to cut mats. I use a Logan 1000 mat cutter - less than $10 at most art supply shops. Be sure to pick up an extra couple of packages of blades - the thing that is most likely to cause problems cutting mats is dull blades, so replace them frequently.
The second thing you will need to cut your mats is something to put behind the mat as your are cutting it. Ideally, a sheet of mat board - but mat board is expensive. Perhaps a sheet of less expensive mat board. I am currently using a sheet of "homosote" from the building supply store.
You will also need a good straight edge. Emphasis on the word good. I am using a Logan straight edge that I picked up at a garage sale. What you need is something that is straight, fairly wide (so you can press you hand down on it to hold it against the board as you are cutting), and that won't flex. Frankly, a scrap of MDF - say 3" wide and however long you need (probably 3') will do a nice job provided the cutting edge is really straight.
And practice. Expect to ruin the first couple of mats - so perhaps you should practice on some smaller prints first (smaller mats).
Now, frames. The best prices for good quality frames is mail order. I have used American Frame many times - their prices are good, they have a great selection, and their service is excellent.
But if you are on a budget, you may be able to find some inexpensive black aluminum frames at an art supply shop. The frames I am thinking of look like the good quality sectional frames from American Frame, but actually are a fixed sized - they don't screw together at the corners. My sense is that they won't last as long (those screw-together metal frames can be reused many times - just insert new work, retighten the corners, and you are good to go), but for your first show, they may be good enough.
Glazing is a choice -- the traditional choice is glass, but in the size you are talking about the glass will be heavy and expensive, and it wears out each time you drop a frame. Plexiglass is lighter and non-breakable, but it attracts dust like crazy. You pay your money and take your choice. Either would come from a glass shop, and you would have to order it in advance and have them cut it to size - check to see how long they will take to determine what fits your schedule. If you use glass, be sure to clean it thoroughly and let it dry completely before assembling your frames.
Good luck with your show.